Our EWC seminar on this Friday, Nov 3, will feature Dr. Kevin Finneran from Clemson University. He will discuss “What do you want me to do with this electron acceptor?” An abstract is included below. Please join us in Mann 304 from 12:50-1:40pm.

The volatility of foreign and domestic petroleum markets has prompted initiatives for the development of alternative liquid energy carriers which have the capacity to accommodate our current transportation infrastructure. Butanol, which has an energy density similar to that of gasoline and can be produced through the fermentation of carbohydrates by solventogenic Clostridia, has been investigated as a supplement or direct replacement to gasoline. However, most butanol fermentations rely on glucose as a feedstock which is in direct competition with our food supply, and this requires the exploration of alternative fermentable substrates.

This study investigated the use of chemical and electrochemical fermentation modifications as “drop-in” strategies to stimulate bacterial solventogenesis (butanol) and the consumption of xylose, which is the second most abundant sugar contained within lignocellulosic biomass, but is generally considered a much lower value substrate because of poor utilization and lower product yields. Monoculture, solventogenic Clostridia and mixed (non-Clostridia) consortia were challenged with electron shuttling compounds and/or a terminal electron acceptor in the form of ferric iron or solid-state graphite electrodes. Results from this study indicated that electron shuttling to ferrihydrite stimulates concomitant increases in metabolite production and xylose consumption for both pure and mixed culture fermentations in which xylose was utilized as the sole fermentable substrate. Mediatorless electrochemical stimulation of solventogenesis and xylose consumption was developed in fermentations challenged with an economical (i.e. lab made), solid-state graphite electrode system. Data presented within this study indicate that extracellular electron transport to terminal electron acceptors has a global, supplementary effect on fermentative bacterial metabolism. In addition, data have demonstrated that xylose plus ferric iron added to environmental media selects for fermentative biomass, rather than Fe(III)-reducing biomass.